+ long double q = - truncl (x / y);
+ long double r = fmal (q, y, x); /* = x + q * y, computed in one step */
+ /* Correct possible rounding errors in the quotient x / y. */
+ if (y >= 0)
+ {
+ if (x >= 0)
+ {
+ /* Expect 0 <= r < y. */
+ if (r < 0)
+ q += 1, r = fmal (q, y, x);
+ else if (r >= y)
+ q -= 1, r = fmal (q, y, x);
+ }
+ else
+ {
+ /* Expect - y < r <= 0. */
+ if (r > 0)
+ q -= 1, r = fmal (q, y, x);
+ else if (r <= - y)
+ q += 1, r = fmal (q, y, x);
+ }
+ }
+ else
+ {
+ if (x >= 0)
+ {
+ /* Expect 0 <= r < - y. */
+ if (r < 0)
+ q -= 1, r = fmal (q, y, x);
+ else if (r >= - y)
+ q += 1, r = fmal (q, y, x);
+ }
+ else
+ {
+ /* Expect y < r <= 0. */
+ if (r > 0)
+ q += 1, r = fmal (q, y, x);
+ else if (r <= y)
+ q -= 1, r = fmal (q, y, x);
+ }
+ }
+ return r;